21010005 has 24 divisors (see below), whose sum is σ = 36536760. Its totient is φ = 11168640.

The previous prime is 21009997. The next prime is 21010013. The reversal of 21010005 is 50001012.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21009997) and next prime (21010013).

It can be written as a sum of positive squares in 4 ways, for example, as 2683044 + 18326961 = 1638^2 + 4281^2 .

It is not a de Polignac number, because 21010005 - 2³ = 21009997 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 18391 + ... + 19499.

It is an arithmetic number, because the mean of its divisors is an integer number (1522365).

Almost surely, 2^21010005 is an apocalyptic number.

It is an amenable number.

21010005 is a deficient number, since it is larger than the sum of its proper divisors (15526755).

21010005 is a wasteful number, since it uses less digits than its factorization.

21010005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1541 (or 1538 counting only the distinct ones).

The product of its (nonzero) digits is 10, while the sum is 9.

The square root of 21010005 is about 4583.6671999612. The cubic root of 21010005 is about 275.9362250253.

Adding to 21010005 its reverse (50001012), we get a palindrome (71011017).

The spelling of 21010005 in words is "twenty-one million, ten thousand, five".